/*
 * @Description: 
 * @Author: charles
 * @Date: 2021-11-19 10:29:15
 * @LastEditors: charles
 * @LastEditTime: 2021-11-19 10:30:37
 */
class Animal {
  name:string;
  age:number;
  sayName?(){ }
}
let a:Animal = new Animal();